V85 Speedometer inaccuracy

[Kiwi_Roy]

My previous ride had a digital speedo, and I found I was concerned with getting it to read correctly. My current 12-y-o Breva has an analogue speedo, and I haven't bothered checking its accuracy because it doesn't worry me in the same way.

The analogue one is approximately correct, but the digital one was exactly wrong!

Gonzo

Am I the only one who can't read the digital speedo in some light conditions, I keep an approximate speed by watching the analog tach needle

[Huzo]

Well it’s really started now..
I’ve decided to produce the tone wheel on the face plate of my lathe. Among other things I needed to arrange the tooling so I could cut 45 slots evenly around the circle.
I started by turning a light groove around the perimeter of the face plate like this.


I then put a layer of tape around the perimeter and used a set of dividers to step out the intervals. The tape was useful in that the process is based on trial and error as you’re approaching the exact distance and with the tape you can see the dots from previous attempts.
I succeeded in achieving 45 equal intervals and it looks like this.





Then I bored the holes you see and produced a locking mechanism so there’ll be no drifting as the holes are milled.






Next step is to set up stops on the cross slide so the cutter will cut the slots the correct length and mount the mill drive.

[GonzoB]

That's nice work.

I don't think I would have been brave enough to drill the faceplate on my lathe (if I had one). I guess it's a lot cheaper than buying a dividing head!

Awaiting updates!

Gonzo

[Huzo]

That's nice work.

I don't think I would have been brave enough to drill the faceplate on my lathe (if I had one). I guess it's a lot cheaper than buying a dividing head!

Awaiting updates!

Gonzo

My Dad bought that lathe in 1969 and left it to me when he passed away 1997..
He would possibly have approved because it was done in the spirit of creating something else and will not affect the plate.
I guess I’ll find out when I get to hell and meet him...
I’d rather face the Devil..

[Huzo]

Is the computer for the abs calibrated to the 48 slots or does it just see pulses and figure the differential between front and rear? 

     Paul B

I just re read that post Paul and with the (slightly) greater knowlege I now have, I’d suggest that the sensors see the tone wheel slots as effectively a straight line.
As each slot passes, it is travelling at a tangent to the perimeter of the circle (mathematically speaking).
I’m bound to admit though, that the computer may have been “told” that 48 slots= 1 revolution.
So my logic is that under the new arrangement, it will take longer for 48 slots to register for any given speed than before, so a 6% lower figure will be generated.

[Huzo]

Ok.
Tomorrow I’ll make an aluminium block to clamp around the machined section of the drill near the chuck.
The 6mm end mill goes into the chuck at centre height with two stops on the cross slide and will be about time to start making slots.


The only drama I can conceive is a lack of rigidity in the chuck, time will tell.
There’s a solution at hand if needs be, but will be a bit of a saga..(as usual).

[KiwiKev]

Ok.
Tomorrow I’ll make an aluminium block to clamp around the machined section of the drill near the chuck.
The 6mm end mill goes into the chuck at centre height with two stops on the cross slide and will be about time to start making slots.


The only drama I can conceive is a lack of rigidity in the chuck, time will tell.
There’s a solution at hand if needs be, but will be a bit of a saga..(as usual).

Sheesh, seems like a lot of work, hope it works out for you.

[Huzo]

Sheesh, seems like a lot of work, hope it works out for you.

Me too mate.
Really though, not counting a bit of shopping for bits and pieces, from taking the wheel out of the bike to what you see, is about 8 hours or so.
Tomorrow I should be ready to cut the first slot if I get a decent run at it..

[KiwiKev]

Me too mate.
Really though, not counting a bit of shopping for bits and pieces, from taking the wheel out of the bike to what you see, is about 8 hours or so.
Tomorrow I should be ready to cut the first slot if I get a decent run at it..

Good luck with that mate, I reckon the ratio of slot to metal (between the slots) isn't critical at all, as long as the electronics gets a pulse it won't care.

[Huzo]

Good luck with that mate, I reckon the ratio of slot to metal (between the slots) isn't critical at all, as long as the electronics gets a pulse it won't care.

That’s comforting to hear from an electronics dude..
I have precision measured the standard width of slots and bars, the ratio is 54/46 %
I have preserved that ratio just in case..
A 6 mm end mill is only a few thou’ from what the calculation called for on the new 45 slot wheel.
I seriously believe the sensor will see the same command as before but at a 6% different rpm.
Also..(I’m hazy on this)
If it is indeed possible to recalibrate the system to allow for a different profile rear tyre, surely that is due to the new rear tyre spinning at a different ratio of front/rear wheel rpm due to it’s different diameter hence rpm.
So.
I’m hoping that when I install the new rear tone wheel, the brain will see a lower rear wheel rpm and sense a rear wheel lock condition. I’m further hoping that it will throw up a command to the ABS as it would if I’d fitted a larger diameter rear tyre.
We know that this can be fixed in the on board calibration via mode button...Yes ?

[Frenchfrog]

fascinating huzo...your going to hate me for saying this but why not just get a sygma digital spedo ??? My kilometre speedo lies like a Sicilian accountant even though it was just overhauled so I spent about 40 euro and supplemented it with the cheaper sygma digital one...I mean it does look a bit odd on a classic seventies guzzi but wtf...at least I know how fast I'm really going
so I do get that!

[Huzo]

fascinating huzo...your going to hate me for saying this but why not just get a sygma digital spedo ??? My kilometre speedo lies like a Sicilian accountant even though it was just overhauled so I spent about 40 euro and supplemented it with the cheaper sygma digital one...I mean it does look a bit odd on a classic seventies guzzi but wtf...at least I know how fast I'm really going
so I do get that!

Why do you say that FF, nothing you could do or say would manage to change my opinion of you...
I don’t hate you any more than I already did....
Seriously mate..
I think we both know why I’m so invested in this. Our winey conversation in your beautiful home in Southern France gave us both an insight into our respective psyche’s..
Why do some people build a beautiful lifestyle in the French hills, when for a lot less “work” they could live in suburbia, yet they take a more circuitous route, to satisfy an urge to solve a problem.
If your new bathroom had inbuilt flaws..(floors?), would you alter it so it ends up lovely like it now does, or get a set of eye covers so you didn’t have to look at it ?
I want to fix the problem mate, not the symptom.
ps
Get that bloody Quota in out of the weather...
And
Keep the window open in the upstairs room, best rest I ever had...

[Frenchfrog]

Yup ...your right and if I didn't have so many other important things to do I would do as you too !!!! I was gutted to find out how inaccurate my speedo was...the mph version isn't anyway near as bad !!!!!

[GonzoB]

Just thought while you're machining the discs....

Is there any way to put an intermediate device between the ECU and the dash? I was thinking something like an Arduino that intercepts all messages and passes them on, but "tweaks" the speed messages to be X% less.

Gonzo

[Huzo]

Just thought while you're machining the discs....

Is there any way to put an intermediate device between the ECU and the dash? I was thinking something like an Arduino that intercepts all messages and passes them on, but "tweaks" the speed messages to be X% less.

Gonzo

Yeah there’s a black box thing that “fixes” it.
Plug and play apparently. I wondered for a while why I didn’t go that route..
Then I stopped wondering.

[Huzo]

Here’s the latest..
I’ve mounted the cutter (so to speak..), I’ve yet to set some stops on the cross slide to ensure accurate repetition of the slot size, but I did a couple free hand because I couldn’t wait..!
Here’s some still shots from the video.

[Huzo]

Today’s exciting episode..
I made the stops for the cross slide and went around with two rows of holes. This is to allow the end mill to terminate in a clean hole at the end of the slot.




Then on to the milling of the slots.

The reason the bottom of the holes look so gummy, is that there’s a piece of 2.5 mm aluminium plate under the steel, to give the milling tool something to drop into when it breaks through the steel.
They’ll need some tidying up post machining, but I’m happy with the repetition aspect so far..I’m half way around.
Jeez I hope the bastard works..

[Frenchfrog]

nice field work mate! It's great what a bit of ingenuity and thought can produce...looks like you nearly there !

[Huzo]

nice field work mate! It's great what a bit of ingenuity and thought can produce...looks like you nearly there !

Yeah, it’s going ok FF.

[Kiwi Dave]

Dunno if your speedo inaccuracy is the same as mine Huzo, but I have noted that mine reads 7 kM too high, regardless of legal speed.  If it had have been a analog speedometer, I could have lifted the glass off the front and bent the needle to correct.

What you're doing is admirable, and I applaud you for your efforts.  But isn't change the ratio just going to fix the calibration at one speed, and therefore displace the others to perhaps further inaccuracy?  That is, if your situation is the same as mine.  If not, ignore everything I said.   

[Huzo]

Dunno if your speedo inaccuracy is the same as mine Huzo, but I have noted that mine reads 7 kM too high, regardless of legal speed.  If it had have been a analog speedometer, I could have lifted the glass off the front and bent the needle to correct.

What you're doing is admirable, and I applaud you for your efforts.  But isn't change the ratio just going to fix the calibration at one speed, and therefore displace the others to perhaps further inaccuracy?  That is, if your situation is the same as mine.  If not, ignore everything I said.   

I don’t think that is correct Dave because there will be a 6% alteration of the pulses per second whether they be 10 per sec or 750 per second.
Now, I’m not holding myself up as an authority on this, if I’m wrong, I’ll crash like a bitch but I won’t die wondering.
If you were correct, an indicated 10 kph would become 4 kph and an indicated 180 would become 174  for example.
One is a 70% inaccuracy and the other a 4% inaccuracy.

[Huzo]

Just in case y’all are still following, I’m up to here.


Tomorrow I’ll trim the O.D. and do the holes. Then it’s on the bike with it and try ‘er out.
This time tomorrow it’ll be in the scrap bin...

[Xlratr]

Looking great!

[Huzo]

Looking great!

Yeah, if it only had to supply the speedo with no front one for the crappy ABS and TC, I’d be quietly confident.
As it is I’m cautiously optimistic.

[Trialsman]

Well it looks good so far, you've certainly done your part.  Hopefully we will read only positive reports after testing.  Merry Christmas.

[Zoom Zoom]

.
This time tomorrow it’ll be in the scrap bin...

That's not very optimistic. Perhaps it works great but you will have to make a mate for the other wheel. Or better yet, it works and all that is left is to recalibrate the puter.

Whatever the outcome, it will not be for lack of trying.

ZZ

[Huzo]

That's not very optimistic. Perhaps it works great but you will have to make a mate for the other wheel. Or better yet, it works and all that is left is to recalibrate the puter.

Whatever the outcome, it will not be for lack of trying.

ZZ

I think it will be the first example.
I am hoping like mad that I can recalibrate though as you say. Thanks for your interest.

[Huzo]

I got onto it again after lunch..
Boring the mounting holes and doing the outside diameter revealed this..



I don’t have six suitable mounting bolts so I’ve gotta’ wait ‘till tomorrow.
But here is the carnage so far..

[Frenchfrog]

very nicely done Huzo...fingers crossed !!

[Huzo]

very nicely done Huzo...fingers crossed !!

Yeah, legs too FF.
(Like my first wife..)